As well-known, many industrial machines and instruments include a feeder to feed a part or all of bodies of them. The feeder is also called a conveyor system or a reciprocating apparatus. As a typical example of them, machine tools etc. are equipped with a feeder for conveying-in work pieces to a working position and conveying-out them out of the working position. Otherwise, there are feeders for supplying raw materials or for conveying-in parts to be assembled to an assembling position and conveying-out the assembled parts out of the assembling position. Thus, the feeders in the mechanical field have been used over a wide range.
There have been various feeders such as a belt-conveyor, a screw type feeder, a cylinder type feeder, a timing belt feeder, a robot or the likes for generally widely known feeders. The particulars of these feeders are as follows;
(Belt Conveyor)
This is adapted to mount conveyance things onto a belt and move the belt by pulleys so as to convey the conveyance things in a continuous manner. This conveying means is most generally used.
(Screw Type Feeder)
This uses a screw such as a trapezoidal screw or a ball screw. This is adapted to mount the conveyance things onto a reciprocating body and feed it by means of the screw thrust. In case of a high precision apparatus, the feeder uses the ball screw as the screw and a servomotor as a power source.
(Cylinder Type Feeder)
This uses an oil pressure system cylinder or a pneumatic cylinder. This is adapted to mount the conveyance things onto the reciprocating body and feed it by means of a force of a piston sliding in a cylinder.
(Timing Belt Type Feeder)
This is adapted to mount the conveyance things onto a timing belt (toothed belt) and move it by toothed pulleys so as to convey them in a continuous manner. This can accomplish the conveyance more precious than the belt conveyor.
(Robot)
This is provided with robot hands having higher operativity such as grasping, moving, releasing (putting) and others. This can have flexibility of directions of conveyance such as upward and downward, rightward and leftward, forward and rearward and rotational direction etc. Many joints can finely control the movement of the robot hands.
Patent Document 1: JP2002-340127
Patent Document 2: JP2002-372119
Patent Document 3: JP2003-311562
The belt conveyor among the aforementioned feeders is inexpensive and suitable for long distance conveyance, but has a poor precision of positioning the conveyance things and a feeding velocity later than the other feeders. In addition thereto, the belt conveyor requires a large installation space proportional to the conveyance distance. The screw type feeder has the higher precision of conveyance because of the use of the polish ball screw and enables the conveyance at middle or high velocity. However, the expensive polish ball screw would cause the apparatus to get also expensive. The screw type feeder is not of space-saving type and also has a shorter conveyance distance, which makes the long distance conveyance difficult. The cylinder type feeder also has the difficulty of long distance conveyance and the problem of expensiveness in the same manner as the screw type feeder. Thus, this cannot accomplish the compactness, which is required for the space saving. Particularly, the cylinder type feeder has the practical problem in which it is difficult to arbitrarily change the conveyance stroke. On the other hand, the timing belt type feeder is more inexpensive than the screw type feeder using the polish ball screw, but gets more expensive than the belt conveyor if it employs highly precious parts in order to expect the high precision of positioning. In addition thereto, the timing belt type feeder can set the conveyance distance longer than the screw type feeder or the cylinder type feeder, but cannot maintain the conveyance distance identical to that of the belt conveyor due to the restrictions on manufacture or the looseness of the belt. Thus, the timing belt type feeder has the shorter conveyance distance than the belt conveyor even though the former is less elongated than the latter. On the other hand, the robot is too expensive even though it has the considerably high precision and functions. In addition thereto, the robot is not suitable for continuous and long distance conveyance.
As apparent from the foregoing, the conventional feeders have merits and demerits. There has been not developed an advantageous and useful feeder having merits collected.
Describing the conventional feeders such as the aforementioned ball screw type feeder and the timing belt type feeder in more details, these feeders have an unavoidable occurrence of fine dust (dust of μm unit or less) caused by friction between the parts of the drive system. There are the fields in which the fine dust is not regarded as questionable and the fields in which the fine dust should be excluded. The fields requiring an extra-high cleanness among the latter fields are the ones of manufacture of liquid-crystal boards and semiconductors.
In order to avoid the occurrence of the fine dust, there have been employed means to heighten an abrasion resistance of the parts or to use grease for reducing the occurrence of the fine dust. Regarding the apparatus, there have been developed a linear servo-actuator having little fine dust occurrence portion as a non-contact power source having electromagnetism power employed. If these means are totally used, predetermined clean atmosphere can be held in the fields of manufacture requiring the extra-high cleanness. However, the linear servo-actuator is too expensive even though it has means good for avoiding the occurrence of fine dust. Therefore, it has been expected to develop means to be able to maintain the cleanness having the same degree as the linear servo-actuator or higher and also to be able to more highly reduce the cost in comparison with the linear servo-actuator.
The technique for reducing the occurrence of the fine dust for the feeder desirably expects all possible measures by multiple means. Since it can improve the yields of the products and reduce the cost for treating the default goods, it will totally improve the economical efficiency.
The precision working apparatus essentially requires the highly precise conveyance as apparent. Therefore, it is an important problem to meet the highly precise conveyance according to its use.
With respect to the feeders, it is also important to maintain the safety and prevent secondary damages by detecting unexpected accidents, which would possibly occur.
It is an object of the invention to provide a feeder to be able to meet the requirements of positioning accuracy, long distance conveyance, remote conveyance, controllability, high precision feeding, high speed feeding, inexpensiveness, simplicity of construction, space saving, weight reduction, measure for dusting and safety for accident.